Moonstone
Feldspar group, Orthoclase / Albite variety (Moonstone) · Semi-Precious Gemstone
Crystal System
Monoclinic; typically found as tumbled, polished, or massive shapes rather than raw crystal form in jewelry applications.
Mineral Group
Silicates (specifically Tectosilicates, Feldspar group)
Chemical Formula
(K,Na)AlSi3O8
Formation Process
Igneous and hydrothermal processes, where molten rock cools slowly allowing alkali feldspars to exsolve into microscopic alternating layers of orthoclase and albite.
About This Crystal
A tumbled, smooth, and polished specimen showing a milky, translucent to semi-translucent body with a characteristic pearly to vitreous luster. It displays subtle internal light scattering known as adularescence.
Physical Characteristics
White to translucent body color with a white streak. It has two directions of good cleavage meeting at nearly 90 degrees, an uneven to conchoidal fracture, and a specific gravity of approximately 2.56 to 2.58. It is brittle with fair to good tenacity.
Optical Properties
Biaxial negative with two refractive indices typically ranging between 1.518 and 1.526. The defining optical property is adularescence—a billowy, glowing light effect caused by light scattering between microscopic lamellar intergrowths.
Hardness & Durability
Origin Region
Sri Lanka, India, Madagascar, Myanmar, Australia, and the United States. Forms in igneous rocks such as pegmatites and granites, as well as in hydrothermal veins.
Hardness & Durability
6 to 6.5 on the Mohs hardness scale. It has distinct cleavage planes making it vulnerable to hard impacts and thermal shock, requiring careful handling in jewelry.
Care & Maintenance
Clean using warm soapy water and a soft cloth. Avoid ultrasonic cleaners, steam cleaners, harsh chemicals, and sudden extreme temperature changes. Store separately to prevent scratching by harder gemstones.
Rarity & Value
Common to Uncommon depending on the quality of adularescence and body clarity. High-end specimens with strong blue adularescence on a clear background command higher prices. Treatments are generally uncommon.
Special Characteristics
Displays notable adularescence (schiller effect), a milky floating light phenomenon caused by the interference of light waves reflecting off alternating microscopic layers of albite and orthoclase.
Lore & History
Historically associated with lunar deities in ancient Roman, Greek, and Indian cultures. Revered as a stone of intuition, inner growth, and emotional balance, frequently linked to the third eye and crown chakras in modern metaphysical practices.